fix(agent): index api_call so RAG tool selection can retrieve it (#3923)

* fix(agent): index api_call so RAG tool selection can retrieve it

api_call exists in FUNCTION_TOOL_SCHEMAS and the agent's system prompt
advertises configured API integrations, but the tool had no entry in
BUILTIN_TOOL_DESCRIPTIONS. RAG tool selection embeds those descriptions and
retrieves the top-K per message, so a tool without one can never be selected:
the agent claims it can call Home Assistant/Miniflux/Gitea/etc. and then
never receives the api_call schema (unless the Personal Assistant
ASSISTANT_ALWAYS_AVAILABLE path applies).

Add a retrieval-rich description for api_call, plus an ast-based parity test
asserting every FUNCTION_TOOL_SCHEMAS tool has an index description so the
next added tool cannot silently drift the same way.

Fixes #3794

* fix(agent): route API-integration intent to api_call at selection time

Addresses review (RaresKeY) on #3923: indexing api_call in the ToolIndex
description was necessary but not sufficient — the #3794 repro ('Use the
api_call tool to call Home Assistant GET /api/states') matched no domain in
_classify_agent_request, classified as low-signal, so the agent loop skipped
retrieval entirely and the schema filter sent only ALWAYS_AVAILABLE
(manage_memory/ask_user/update_plan). api_call never reached the model.

- _classify_agent_request: detect API-integration intent (api_call,
  integration(s), Home Assistant/Miniflux/Gitea/Linkding/Jellyfin) -> new
  'integrations' domain, so the turn is no longer low-signal.
- _DOMAIN_TOOL_MAP['integrations'] = {api_call}: deterministically seeds
  api_call into relevant tools after retrieval, independent of embeddings.
- _DOMAIN_RULES['integrations']: rule pack (required — _domain_rules_for_tools
  indexes _DOMAIN_RULES[domain] directly).
- tool_index _KEYWORD_HINTS: parity hint for the retrieval / keyword-fallback
  paths.
- Regression drives the real classifier -> domain-map -> FUNCTION_TOOL_SCHEMAS
  filter chain and asserts api_call is advertised for the #3794 prompt.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/agent_loop.py

@@ -267,6 +267,10 @@ _DOMAIN_RULES = {
 - Use `resolve_contact` to look up a contact's email or phone number by name. Searches the CardDAV address book and sent email history.
 - Use `manage_contact` to list, add, update, or delete contacts in the address book.
 - Do NOT use `manage_memory` for contact lookups — contact details live in the address book, not memory.""",
+    "integrations": """\
+## Integration/API rules
+- To query or control a configured service integration (Home Assistant, Miniflux, Gitea, Linkding, Jellyfin, or any other registered service), use `api_call` with the integration name, HTTP method, path, and optional JSON body.
+- Do not use shell, curl, or `app_api` to reach a user's connected integration when `api_call` is available.""",
 }
 
 _DOMAIN_TOOL_MAP = {
@@ -280,6 +284,7 @@ _DOMAIN_TOOL_MAP = {
     "files": {"bash", "python", "read_file", "write_file", "edit_file", "grep", "glob", "ls", "get_workspace"},
     "settings": {"manage_settings", "manage_endpoints", "manage_mcp", "manage_webhooks", "manage_tokens", "app_api"},
     "contacts": {"resolve_contact", "manage_contact"},
+    "integrations": {"api_call"},
 }
 
 def _domain_rules_for_tools(tool_names: set) -> list[str]:
@@ -815,6 +820,15 @@ def _classify_agent_request(messages: List[Dict], last_user: str) -> Dict[str, o
         domains.add("settings")
     if has(r"\b(contact|contacts|phone|phone number|address book|vcard)\b"):
         domains.add("contacts")
+    # API-integration intent — calling a configured service via the api_call
+    # tool. Without this the #3794 repro ("Use the api_call tool to call Home
+    # Assistant GET /api/states") matched no domain, classified as low-signal,
+    # and the tool never reached the schema filter. Detect it explicitly so the
+    # "integrations" domain seeds api_call deterministically (see
+    # _DOMAIN_TOOL_MAP), independent of embedding retrieval.
+    if has(r"\bapi[ _]call\b", r"\bintegrations?\b",
+           r"\b(?:home ?assistant|miniflux|gitea|linkding|jellyfin)\b"):
+        domains.add("integrations")
 
     low_signal = not continuation and not domains
     return {